The present invention relates to a controlled permeability composite stopper for stopping bottles, in particular bottles of wine, having a body made from a compressible material such as cork, fitted with complementary means forming a seal at least at the end facing toward the content of the bottle.
Stoppers of the above type are described in French patents Nos. 983 488, 1 068 263, 1 100 335, 1 338 657, 1 573 650, 2 644 142 and 2 736 036 and European patent application EP-A-0 532 367, for example. In the above documents, the complementary seal means can be sheets, films, coatings, disks, etc. of synthetic material, rubber, elastomer, for example silicone elastomer, covering at least the whole of the end face of the stopper facing toward the content of the bottle to be stopped.
The use of cork in stopping wines is related to the exceptional qualities of the material, namely its virtual freedom from rotting, compressibility, resilience, sealing effect, easy machining from raw cork-oak bark, aptitude for gaseous exchange, durability, etc.
However, cork is also the cause of certain organoleptic problems due to interaction with the wine. Also, given the fact that it is machined, the tolerances that apply and defects that are sometimes difficult to detect, despite rigorous inspection, a cork stopper is sometimes incapable of providing a total liquid seal at the cork-glass interface, whence the well-known xe2x80x9cleaky bottlexe2x80x9d phenomenon.
The proposals in the patents cited above are not satisfactory, in particular because the complementary means provided on at least one end face of the stopper cause problems when the stopper is pushed into the bottle neck. Because the means referred to cover the whole of the end face of the stopper facing toward the content of the bottle, it is the material from which the complementary means are made that comes into contact with the end of the neck when the stopper is pushed in after compressing it radially. Because the material from which the complementary means are made is incompressible, unlike the cork constituting the body of the stopper, the complementary means are not subjected to the same deformation as the body of the stopper, with the attendant risk of imperfections such as creasing, cracking, peeling, etc. In this regard, it should be noted that stopping a bottle includes an operation of radially compressing the stopper, which has a diameter of 24 mm for still wine or 31 mm for sparkling wine, to a diameter of 15.5 mm, in jaws, the compressed stopper then being pushed into the bottle neck, where it expands to the inside diameter of the neck, which is 19 mm for a still wine or 17 mm for a sparkling wine.
Pressing in stoppers compressed in this way is not a problem if the stoppers are made entirely of cork.
It is a problem, however, if the end face of the stopper facing toward the content of the bottle to be stopped is covered with complementary means in the form of a synthetic material sheet, film, disk or coating.
It is then the complementary means that first come into contact with the end of the neck and are stressed to the point of being damaged. Also, the material from which the complementary means are made has a high coefficient of friction relative to the glass of the bottle neck, unlike the cork of conventional stoppers, which are incidentally often treated to slide more easily.
For all the above reasons, the composite stoppers disclosed in the documents previously cited have in practice not become the norm for stopping wine.
The present invention is directed to a composite stopper which remedies the disadvantages of the usual stoppers made entirely of cork and also the disadvantages of the composite stoppers disclosed in the prior art patents cited above.
A composite stopper in accordance with the invention for stopping the neck of bottles, in particular bottles of wine, comprises a body made from a compressible material such as cork, fitted with complementary means forming a seal at least at its end facing toward the content of the bottle to be stopped, characterized in that said means comprise a member made from a substantially incompressible elastomer, virtually completely filling a circular section cavity formed concentrically in an end face of the stopper body so that a ring of the end face of the stopper body remains around said cavity, which has a volume such that said member, due to compression of the stopper body during stopping, is elastically deformed forward of said end face, after stopping, so as to establish after stopping, forward of said end face of the stopper body, a seal covering the whole of said end face and in contact with the inside face of the bottle neck.
In accordance with the present invention, before the stopper is compressed, the substantially incompressible elastomer member filling the cavity in the end face does not cover the whole of the end face of the stopper, but leaves a ring of cork between its outside edge and the outside edge of the end face.
The ring of cork enables the bottling operation to be carried out in the usual way, without modification. Because the relaxation time of the elastomers used is greater than one second and, in the usual bottling machines, the time between compressing the stoppers and pushing them is generally less than one second, the elastomer does not have time to deform completely, in response to the compression of the body of the stopper, before the stopper is pushed into the bottle neck. When the stopper is pressed in, it is therefore the outside edge of the ring of cork which comes into contact with the top of the neck of the bottle, and the conditions under which the stopper slides in the neck are therefore the same as with stoppers made entirely of cork.
In other words, the stopping operation is in no way modified by the presence of the elastomer member on the stopper according to the invention.
The volume (diameter and depth) of the cavity filled with elastomer can vary, in particular as a function of the degree of compression of the stopper body, which varies according to the type of wine to be stopped. However, the cavity is preferably at least 1 mm deep at its deepest point, before compression.
The elastomer member is shaped to leave a ring with a (radial) width of at least 1 mm on the end face of the stopper body before compression of the stopper body.
Said cavity can have a substantially cylindrical shape, for example, but it preferably has a divergent shape, i.e. a diameter that increases from the bottom toward the open side.
The elastomer constituting the member filling said cavity is preferably a foodstuffs grade silicone elastomer.
The elastomer member is preferably molded and cross-linked before it is fitted into the cavity, but can also be obtained by molding and cross-linking the raw elastomer in the cavity of the stopper body.
In one embodiment the elastomer can be an elastomer permeable to small gas molecules such as H2, N2, O2, CO2 and impermeable to large molecules such as molecules with aromatic cycles, including those responsible for the xe2x80x9ccorked tastexe2x80x9d. The seal consisting of the elastomer member therefore does not degrade in any way the exchange of small-molecule gases, leaving the cork of the stopper body to fulfill its usual role of controlling gas exchange on its own.